To date, there are many devices able to periodically re-establish imperviousness between two elements via the repetition of a relative movement of two mechanical pieces which clamp a gasket and in particular slide valves, clack valves, cocks and inspection doors with periodical opening and closing. In some of these devices, the gasket is metallic and elastic and is compressed between bearings made of an identical or different metal. Certain criteria, such as fire-resistance, a high working temperature and the need to obtain a high vacuum, may in fact impose that other materials be excluded.